How can I encrypt a querystring in asp.net?

Question

I need to encrypt and decrypt a querystring in ASP.NET.

The querystring might look something like this:

http://www.mysite.com/report.aspx?id=12345&year=2008

How do I go about encrypting the entire querystring so that it looks something like the following?

http://www.mysite.com/report.aspx?crypt=asldjfaf32as98df8a

And then, of course, how to I decrypt it? What's the best encryption to use for something like this? TripleDES?

Answer 1

Here is a way to do it in VB From: http://www.devcity.net/Articles/47/1/encrypt_querystring.aspx

Wrapper for the encryption code: Pass your querystring parameters into this, and change the key!!!

Private _key as string = "!#$a54?3"
Public Function encryptQueryString(ByVal strQueryString As String) As String
    Dim oES As New ExtractAndSerialize.Encryption64()
    Return oES.Encrypt(strQueryString, _key)
End Function

Public Function decryptQueryString(ByVal strQueryString As String) As String
    Dim oES As New ExtractAndSerialize.Encryption64()
    Return oES.Decrypt(strQueryString, _key)
End Function

Encryption Code:

Imports System
Imports System.IO
Imports System.Xml
Imports System.Text
Imports System.Security.Cryptography

Public Class Encryption64
    Private key() As Byte = {}
    Private IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF}

    Public Function Decrypt(ByVal stringToDecrypt As String, _
        ByVal sEncryptionKey As String) As String
        Dim inputByteArray(stringToDecrypt.Length) As Byte
         Try
            key = System.Text.Encoding.UTF8.GetBytes(Left(sEncryptionKey, 8))
            Dim des As New DESCryptoServiceProvider()
            inputByteArray = Convert.FromBase64String(stringToDecrypt)
            Dim ms As New MemoryStream()
            Dim cs As New CryptoStream(ms, des.CreateDecryptor(key, IV), _
                CryptoStreamMode.Write)
            cs.Write(inputByteArray, 0, inputByteArray.Length)
            cs.FlushFinalBlock()
            Dim encoding As System.Text.Encoding = System.Text.Encoding.UTF8
            Return encoding.GetString(ms.ToArray())
        Catch e As Exception
            Return e.Message
        End Try
    End Function

    Public Function Encrypt(ByVal stringToEncrypt As String, _
        ByVal SEncryptionKey As String) As String
        Try
            key = System.Text.Encoding.UTF8.GetBytes(Left(SEncryptionKey, 8))
            Dim des As New DESCryptoServiceProvider()
            Dim inputByteArray() As Byte = Encoding.UTF8.GetBytes( _
                stringToEncrypt)
            Dim ms As New MemoryStream()
            Dim cs As New CryptoStream(ms, des.CreateEncryptor(key, IV), _
                CryptoStreamMode.Write)
            cs.Write(inputByteArray, 0, inputByteArray.Length)
            cs.FlushFinalBlock()
            Return Convert.ToBase64String(ms.ToArray())
        Catch e As Exception
            Return e.Message
        End Try
    End Function

End Class